The invention relates to a method for the production of free-flowing additives, and the additives that can be obtained with the method.
The production and use of additives, such as hydrolysis protection additives, is known in principle. Especially in the area of polyesters, stabilization against hydrolysis is required for very many application purposes.
Accordingly, U.S. Pat. No. 6,069,204 describes a mono-fiber made from a mixture of polyester and multivalent alcohol of a 1,4-cyclohexane dimethanol, a polyamide, and a polyolefine. For stabilization against hydrolysis, bis-(2,6-diisopropylphenyl)-carbodiimide, as well as other substances, can be added.
The use of carbodiimides as hydrolysis stabilizers is also known from EP 1 425 443, which discloses branched polyethylene terephthalate mono-fibers and/or filaments. One feature of EP 1 425 443 is directed at the branched-chain polyethylene terephthalates being stabilized by an effective amount of a hydrolysis stabilizer additive which also are present in the form of mono-filaments. These hydrolysis stabilizer additives undergo a chemical reaction with the terminal carboxyl groups.
A further hydrolysis stabilizer is described in JP 2006249152 A. Here, a stabilizer is concerned that is present in a resin that can be decomposed biologically.
A further hydrolysis stabilizer is mentioned in JP 2004277931 A; herein also a carbodiimide compound is concerned that undergoes a reaction with the terminal carboxyl groups of a polymer fiber. GB 1 485 294 also refers to polyester filaments and/or a method for the production thereof, whereby, as before, it is essential that stability of the fibers against hydrolysis is provided, for which purpose a carbodiimide stabilizer is allowed to undergo a reaction with the carboxyl groups of the starting resin.
Finally, WO 03/010370 also relates to stabilized polymer compositions and mono-filaments that are made from them and are stabilized against hydrolysis. Again, the stabilizer is a monomeric or polymeric carbodiimide.
Especially carbodiimide stabilizers are disadvantageous in that the product bakes together after some period of storage such that the further processing is made significantly more difficult and the quality of the product is affected adversely. Excipients have been added, such as, e.g., silica dust (Aerosil®), in order to overcome this problem, but this is undesirable since the excipients also end up in the finished product.